400 ppm Carbon Dioxide Exceeded At South Pole

Atmospheric carbon dioxide concentrations at the South Pole exceeded 400 ppm on 23 May for the first time, according to data from NOAA. Image shows the US National Science Foundation's observatory at the South Pole where the measurements were made. Courtesy: NOAA

Atmospheric carbon dioxide concentrations at the South Pole exceeded 400 ppm on 23 May for the first time, according to data from NOAA

From the US National Oceanographic and Atmospheric Administration (NOAA)

The Earth passed another unfortunate milestone May 23 when carbon dioxide surpassed 400 parts per million (ppm) at the South Pole for the first time in 4 million years.

The South Pole has shown the same, relentless upward trend in carbon dioxide (CO2) as the rest of world, but its remote location means it’s the last to register the impacts of increasing emissions from fossil fuel consumption, the primary driver of greenhouse gas pollution.

“The far southern hemisphere was the last place on earth where CO2 had not yet reached this mark,” said Pieter Tans, the lead scientist of NOAA’s Global Greenhouse Gas Reference Network. “Global CO2 levels will not return to values below 400 ppm in our lifetimes, and almost certainly for much longer.”

Over the course of the year,CO2 levels rise during fall and winter and decline during the Northern Hemisphere’s summer as terrestrial plants consume CO2 during photosynthesis. But plants capture only a fraction of annual CO2 emissions, so for every year since observations began in 1958, there has been moreCO2 in the atmosphere than the year before.

Last year’s globalCO2 average reached 399 ppm, meaning that the global average in 2016 will almost certainly surpass 400 ppm. The only question is whether the lowest month for 2016 will also remain above 400.

South Pole carbon dioxide levels hit record. Daily average carbon dioxide readings at the South Pole from 2014 to present, as recorded by NOAA’s greenhouse gas monitoring network. Courtesy: NOAA

Upward trend continues past 400 ppm

And the annual rate of increase appears to be accelerating. The annual growth rate of atmosphericCO2 measured at NOAA’s Mauna Loa Observatory in Hawaii jumped 3.05 ppm during 2015, the largest year-to-year increase in 56 years of monitoring. Part of last year’s jump was attributable to El Nino, the cyclical Pacific Ocean warming that produces extreme weather across the globe, causing terrestrial ecosystems to lose stored CO2 through wildfire, drought and heat waves.

Last year was the fourth consecutive year that CO2 grew more than 2 ppm – which set another record. This year promises to be the fifth.

“We know from abundant and solid evidence that the CO2 increase is caused entirely by human activities,” Tans said. “Since emissions from fossil fuel burning have been at a record high during the last several years, the rate of CO2 increase has also been at a record high. And we know some of it will remain in the atmosphere for thousands of years.”